Thickened oil development method for breaking through fireflood interlayer based on stratum adsorptive combustion improver

Abstract

The invention discloses a thickened oil development method for breaking through a fireflooding interlayer based on a combustion improver with stratum adsorbability. Selecting a heavy oil reservoir, identifying and confirming a low-permeability interlayer area, and delimiting a target injection area and an injection well group; injecting a combustion improver composition with stratum adsorbability into the interlayer area, and after adsorption is completed, implementing front air pre-injection to activate and catalyze the oxidation capacity of the combustion improver; an ignition agent is continuously injected through the gas injection well to initiate an in-situ combustion reaction; gas injection is maintained, parameters such as combustion temperature and product components are monitored, and stable propulsion of the combustion front edge is controlled. The combustion improver composition comprises an oxidant, a combustion improver, an inorganic catalyst, a catalyst with stratum adsorbability, an emulsifier / surfactant, a polymer adsorbent, a solvent and a pH regulator. The stratum adsorbability of the combustion improver is improved, the combustion improver is enriched at the adsorption site of the interlayer part, high-temperature and high-pressure reaction is generated after ignition, the interlayer structure is broken through, and heat channel breaking through and stable combustion wave propelling are achieved.

Description

Technical Field

[0001] This invention belongs to the technical field of oil and gas field development engineering, specifically relating to a method for developing heavy oil through fire-driven interlayers based on formation adsorbent combustion-supporting agents. Background Technology

[0002] In-situ Combustion (ISC), also known as underground combustion, is an important enhanced oil recovery (EOR) technology, particularly suitable for the later-stage development of heavy and extra-heavy oil reservoirs.

[0003] The basic principle of reservoir combustion flooding is as follows: Under formation conditions, crude oil in the reservoir is used as fuel, and air or a combination of gases is used as an oxidizer. Partial combustion of the crude oil is initiated by ignition within the reservoir. During this process, light crude oil undergoes distillation upon heating. The light oil and flue gas generated by combustion, along with water vapor formed by water evaporation in the reservoir, all contribute to the driving effect. Simultaneously, the residues of heavy components after pyrolysis generate coke under high-temperature conditions, which serves as continuous fuel to maintain the advance of the combustion front. The heat released by combustion, superheated steam, and flue gas work together to drive unburned crude oil towards the production well, thereby expanding the affected area and improving recovery. Therefore, the stable advancement of the combustion front and the affected volume during fire flooding have a significant impact on the effectiveness of fire flooding development. Reservoir interlayers refer to relatively impermeable rock layers distributed within the reservoir or between adjacent reservoirs that can completely block or partially affect the movement of underground fluids.

[0004] Oil reservoir interlayers can be classified into argillaceous, calcareous, and calcareous-argillaceous interlayers based on their lithology, exhibiting relative differences in permeability to the surrounding reservoir. Interlayers are relatively thin, generally a dozen centimeters, with some reaching tens of centimeters in thickness. Their lateral distribution is unstable and their coverage area is small. In contrast, the thickness of diaphragms is generally several to tens of meters, with a very stable lateral distribution and a wide coverage area. These interlayers have a significant impact on the flow, distribution, and development effectiveness of oil and gas. Their low thermal conductivity and poor permeability significantly hinder air injection, heat conduction, and combustion wave propagation, acting as "thermal barriers" or "combustion path blockers" during fire flooding, and are a key manifestation of reservoir heterogeneity.

[0005] Since its inception, oil reservoir combustion technology has been widely used in the later stages of reservoir development due to its high oil displacement efficiency, high recovery rate, and wide reservoir adaptability. It works by igniting the oil reservoir, propelling the combustion front forward, heating the crude oil, reducing its viscosity, and generating gas to drive oil flow. However, when thick or highly continuous interlayers exist within the oil reservoir, they can create a barrier to the vertical propagation of the high-temperature front. This alters the combustion path, causing the combustion front to stagnate or deviate before the interlayer, ultimately leading to a decrease in recovery rate. Furthermore, the oil layer above the interlayer experiences slow temperature rise due to poor heat transfer, failing to form an effective combustion zone. This results in reduced reservoir utilization, uneven combustion, and limited oil-producing areas, significantly restricting the effectiveness of fire-driven development.

[0006] Despite significant achievements by engineers in the study of fire-driven oil reservoirs, conventional fire-driven development techniques are mostly applicable to formations with relatively weak heterogeneity. For development blocks with strong heterogeneity and interlayer obstruction, the main current methods include: adjusting the well network to avoid interlayers, using horizontal wells to cross layers, and localized strong gas injection to enhance penetration. However, these methods are complex to implement, costly, have poor adaptability, and cannot actively destroy or modify the interlayer structure. Summary of the Invention

[0007] The purpose of this invention is to address the problems of combustion inhibition caused by reservoir interlayers, leading to easily blocked combustion fronts, disconnected thermal drive channels, and low recovery rates. This invention provides a method for developing heavy oil through fire-driven interlayers based on a combustion-enhancing agent system with formation adsorption properties. This method improves the formation adsorption properties of the combustion-enhancing agent, enriching it at adsorption sites within the interlayer. Upon ignition, a high-temperature, high-pressure reaction occurs, breaking through the interlayer structure and achieving the opening of thermal channels and stable propagation of the combustion wave.

[0008] The technical solution of this invention is as follows: A method for developing heavy oil in breakthrough fire-driven interlayers based on formation-adsorbable combustion improvers includes the following steps:

[0009] (1) Selection of reservoirs for development: Based on the geological characteristics and current development status of the reservoirs, the reservoirs suitable for this development method are preliminarily screened according to the following conditions: the reservoirs are heavy oil reservoirs that have undergone multiple rounds of steam thermal recovery and are in the middle and late stages of development; the structures are closed; the burial depth is 500-1500 m; the permeability is >50 mD; the porosity is >20%; the remaining oil saturation is >35%; the oil layer thickness is >10 m; the crude oil viscosity is 100 mPa·s–100000 mPa·s; and the crude oil density is 0.90-0.99 g / cm³. 3 .

[0010] (2) Interlayer identification: Based on seismic data, well logging data and block strata modeling, and with well logging parameters as the main factor, identify and confirm low-permeability interlayer zones such as muddy interlayers, physical property interlayers, and calcareous interlayers in the reservoir, delineate the target injection area, and divide the injection well group using the original injection and production well network.

[0011] The specific steps for identifying low-permeability interlayer zones in step (2) are as follows: Collect a complete set of logging curves including natural gamma, spontaneous potential, depth, resistivity, sonic transit time, and density, and uniformly correct the well depth, well inclination, and wellhead reference. Identify low-permeability interlayers based on sonic transit time > 120 μs / ft, density > 2.2 g / cm³, natural gamma > 60 API, and resistivity > 80 Ω·m.

[0012] Specifically, for clay interlayers, due to their high clay content, the natural gamma curve value is generally between 70-85 API; the density curve value is generally around 2.25 g / cm³. 3 The values ​​are around 3%, while the resistivity curve values ​​are relatively small, at a few ohm-meters; the well logging interpretation porosity value is less than 3%, and the well logging interpretation permeability value is less than 20 mD.

[0013] Specifically, for calcareous interlayers, the main characteristics are a natural gamma curve value between 60-80 API, with small and moderate differences in amplitude between shallow and deep sides; the main feature in the curve morphology is the appearance of a "calcium peak" in the density curve, where the density value increases sharply, typically around 2.5 g / cm³. 3 The calcium interlayer is particularly dense, with a permeability curve value of less than 10 mD.

[0014] Specifically, for the physical property interlayers, the natural gamma curve value is smaller than that of the argillaceous interlayers but larger than that of the pure sandstone section, ranging from 50 to 70 API; the density curve value is moderate, ranging from 2.1 to 2.3 g / cm³. 3 Between; resistivity curve values ​​are moderate, porosity is less than 15%, and permeability is less than 500 mD.

[0015] In addition, seismic data for this block, including reflection wave data and velocity models, can be acquired. The seismic data can then be denoised and outliers removed. Key attributes, including reflection intensity, phase, and frequency, can be extracted from the seismic data. Attribute analysis can then be used to identify potential low-permeability interlayers. Geological modeling of this block can also directly identify existing interlayers.

[0016] (3) Combustion accelerator injection: A liquid composition of combustion accelerator with clay adsorption properties is injected into the interlayer region. The combustion accelerator preferentially adsorbs and accumulates on the surface or in the pore throat structure of clay and calcareous interlayers, thereby reducing local thermal resistance, catalyzing the combustion reaction, and improving the interlayer breakthrough efficiency. After the combustion accelerator adsorption is completed, pre-injection of air is carried out to activate the oxidation capacity of the catalytic combustion accelerator.

[0017] Specifically, the combustion aid in step (3) includes an oxidant liquid and a fuel emulsion; the oxidant liquid includes an ignition oxidant and a polymer adsorbent; the fuel emulsion includes fuel, emulsifier and catalyst.

[0018] The ignition oxidant, introduced with the injected fluid, enters the pore throat of the muddy / calcareous interlayer, where it is partially adsorbed and fixed, preferentially residing within the interlayer. Under underground reservoir conditions with a metal catalyst and continuous oxygen supply, an exothermic oxidation reaction zone is formed first in the interlayer, releasing oxygen, reducing the interlayer's thermal resistance, and simultaneously maintaining the leading-edge reaction. Preferred ignition oxidants include potassium permanganate (KMnO4), ammonium nitrate (NH4NO3), potassium nitrate (KNO3), hydrogen peroxide (H2O2), and potassium chlorate (KClO3).

[0019] Fuel: Entering the pore throat of the muddy / calcareous interlayer along with the injected fluid, it is partially adsorbed and fixed, preferentially remaining within the interlayer. During combustion, it serves as part of the heat source, lowering the ignition temperature of the underground crude oil, increasing its mobilization, and promoting more complete combustion and conversion, thereby improving the interlayer breakthrough efficiency. Diesel fuel is preferred.

[0020] Catalysts: Catalyze redox reactions, increasing reaction rates and oxygen utilization, and lowering the ignition temperature. These include inorganic salt catalysts and nano-oxide catalysts with formation adsorption properties. Inorganic salt catalysts are metal chlorides, preferably ferric chloride (FeCl3) and copper chloride (CuCl2). Nano-oxide catalysts with formation adsorption properties include nano-Fe2O3, nano-SiO2, and nano-Co3O4.

[0021] Emulsifier / surfactant: Resistant to salt and high underground salinity, emulsifies heavy oil, reduces heavy oil viscosity, and improves oil-water interfacial tension and foam stability; it can also be adsorbed on pore throat surfaces to improve rock wettability. The preferred emulsifier is a composite petroleum sulfonate, specifically cocamidopropyl betaine (C...). 19 H 38 N2O3), sodium dodecylbenzenesulfonate (C 18 H 29 NaO3S), rhamnolipid (C 26 H 48 O9). Specifically, compound petroleum sulfonates are produced through processes such as cracking and fractionation of heavy oil in oil fields. The active components include alkylbenzene sulfonates, alkylnaphthalene sulfonates, etc., with molecular weights generally between 200 and 400.

[0022] Polymer adsorbents can thicken and block high-permeability channels, facilitating the delivery of combustion-supporting agents to low-permeability interlayers. Simultaneously, the polymer interacts with the mineral surface, producing an adsorption effect. Water-soluble polymer adsorbents, such as polyacrylamide and hydrolyzed polyacrylamide, are preferred.

[0023] In this invention, polymer adsorbents, metal nano-oxides with stratum adsorption properties, and some biosurfactants also have stratum adsorption properties, promote the enrichment of combustion aids at the adsorption sites in the interlayer, and generate a high-temperature and high-pressure reaction after ignition, breaking through the interlayer structure.

[0024] Furthermore, the aforementioned combustion aids also include a solvent: distilled water; and a pH adjuster: hydrochloric acid (HCl).

[0025] The pH of the combustion-supporting liquid is 4.0-6.0.

[0026] The combustion improver of this invention reduces ignition temperature, increases interlayer breakthrough efficiency, enhances oxygen utilization, stabilizes the combustion front, and improves the fluidity of heavy oil.

[0027] Furthermore, the combustion improver composition employs an AB dual-liquid system, sequentially injected and mixed underground. Liquid A is an oxidant liquid, including an ignition oxidant, a polymer adsorbent, and distilled water as a solvent. Liquid B is a fuel emulsion, including the main fuel, emulsifier, and catalyst. Liquid A (oxidant liquid) is injected first, and its carried polymers preferentially allow it to enter and remain in the high-permeability layer. Subsequently, Liquid B (fuel emulsion) is injected, and its adsorbent components (adsorbent surfactants, nano-sized metals, etc.) cause the fuel to be more evenly distributed on the surface of the pores already occupied by Liquid A. The two liquids displace and mix with each other in the formation pores.

[0028] Furthermore, the combustion improver includes an oxidant liquid and a fuel emulsion, wherein the oxidant liquid includes an ignition oxidant and a polymer adsorbent; the fuel emulsion includes fuel, an emulsifier, and a catalyst; the combustion improver comprises, by mass percentage: 10-30% ignition oxidant, 0.5-2% polymer adsorbent, 20% fuel, 2-3% emulsifier, 0.01-0.3% catalyst, 0.1-3% pH adjuster, and the balance being water.

[0029] The specific injection conditions for the combustion-supporting agent in step (3) are as follows: The injection fluid temperature is 40-60 ℃, specifically determined by the reservoir temperature and the temperature required to maintain the uniformity and stability of the combustion promoter; the injection pressure is 1.1–1.3 times the formation pressure; the injection rate is 20-50 m³ / h / well, and the total injection volume is 0.2-0.5 PV. For fractured areas, the concentrations of surfactants, polymers, and rock-adsorbing catalysts can be appropriately increased to enhance wetting and adsorption capabilities.

[0030] The specific steps for injecting the combustion-supporting agent in step (3) are as follows: Injection wells are divided into blocks, and gas is injected from injection wells in an intermittent manner, lasting 3–6 hours each time, with the injection pressure not exceeding the reservoir fracture pressure. After injection, the wells are shut down and allowed to stand for 5–7 days to allow formation adsorption. Adsorption efficiency can be assessed by monitoring the flowback fluid concentration; if the combustion promoter flowback rate is <10%, adsorption is considered successful. Then, pre-injection of air is performed, with a total injection volume of 3–5 PV. Before initiating the main fire drive, a reservoir pressure recovery test is conducted to ensure the existence of good heat and mass transfer channels in the interlayer region.

[0031] (4) Ignition and Combustion: After the above steps are completed, fire-driven oil recovery can be carried out by ignition. Ignition agent is continuously injected through the gas injection well to initiate an in-situ combustion reaction. The combustion aid reacts violently in the interlayer area, forming an instantaneous high temperature and high pressure environment, which ruptures the interlayer structure;

[0032] The ignition agent in step (4) is a mixture of 90% air by volume and 10% oxygen by volume with a purity of 99.9%, at a temperature of 30–40°C.

[0033] The specific steps for in-situ combustion reaction initiated by injecting igniter in step (4) are as follows: A mixture of oxygen and air is continuously injected through an injection well using an air compressor. The injection volume is greater than 2 PV, the injection pressure is less than the reservoir fracture pressure, and the injection rate is 500-1000 m³ / h. In the initial stage of the ignition reaction, the downhole temperature and reaction are monitored in real time using temperature probes and pressure monitoring equipment. When the combustion front reaches the vicinity of the interlayer, secondary ignition is performed near the interlayer to create a high-pressure combustion environment, ensuring the interlayer fractures.

[0034] (5) Combustion front advancement and dynamic control: Maintain gas injection, monitor parameters such as combustion temperature and product composition, and achieve stable control of wavefront advancement.

[0035] The specific steps of wavefront propagation and dynamic control in step (5) are as follows: After the reservoir is ignited, a mixture of oxygen and air is continuously injected to prolong the combustion reaction and form a stable combustion front. Specifically, the injection pressure is 1.1–1.3 times the formation pressure, and the initial injection rate is set at 500 m³ / h, gradually increasing as temperature and pressure change. During combustion, the wellhead temperature is monitored in real time. By segmenting and temporarily adjusting the injection points of the injection well, the direction of combustion front advancement is adjusted to maintain the combustion front temperature within the range of 350℃–650℃, preventing excessively high temperatures that could cause formation instability and uneven combustion front expansion. The gas composition of the production well is analyzed in real time, and the sufficiency of the combustion reaction is judged by the CO₂ / CO ratio: a CO₂ / CO ratio in the range of 4:1–10:1 indicates a relatively complete combustion reaction. The advancement speed of the combustion front should be controlled between 0.5–2.5 m / h. If slow regional advancement occurs, the injection rate and oxygen concentration are increased.

[0036] This invention applies to heavy oil reservoirs in the post-tertiary oil recovery stage. Compared to conventional light oil reservoirs, heavy oil reservoirs are characterized by higher viscosity, poorer fluidity, and greater difficulty in extraction. To address these issues, thermal recovery technologies are commonly employed in the development of heavy oil reservoirs, such as steam drive, steam huff and puff, and steam-assisted gravity drainage. However, these technologies face numerous problems and challenges in the later stages of tertiary oil recovery in heavy oil reservoirs, including high heat loss, high production costs, and poor economic returns. Therefore, in the final stages of reservoir development, methods such as reservoir incineration are generally chosen for development.

[0037] These types of reservoirs typically have high remaining oil saturation and significant exploitation potential. The structurally closed geological conditions help reduce gas spillage losses, limit gas flow paths, and enhance the stability and effectiveness of thermal flooding reactions. The appropriate burial depth of 500-1500 m is chosen because shallow reservoirs have lower pressure and temperature, making it difficult to form closed structures and increasing the difficulty of ignition and combustion. Deep reservoirs, on the other hand, increase the difficulty and cost of injection and production, resulting in poor economic returns. Formations with high permeability and large porosity facilitate the adsorption of combustion promoters, the supply of oxygen and combustion promoters during combustion, and the propagation of the heat front, thereby improving fire flooding efficiency. Simultaneously, high-viscosity crude oil is usually developed using thermal recovery technologies, and the recovery rate is significantly affected by viscosity. Reservoir combustion technology, with its high-temperature viscosity reduction, pyrolysis, and driving capabilities, can significantly reduce oil viscosity and decrease extraction costs.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] This invention utilizes polymers, surfactants, and nano-oxides with formation adsorption properties to enhance the formation adsorption of flame retardants. Among these, the polymer adsorbent plays a crucial role in the fire flooding process: it significantly accelerates the local temperature response, promotes rapid breakthrough of interlayers, and improves oil recovery by enhancing the retention of oxidants in the porous medium, promoting the uniform distribution of reactants, and especially constructing stable reactant enrichment zones near interlayers.

[0040] The present invention describes a method for developing heavy oil reservoirs by breaking through interlayers in fire-driven flooding. This method utilizes the thermal energy release of highly reactive and adsorbent fire-promoting agents to disrupt the low-permeability interlayer structure of the reservoir, providing a more stable and efficient heat conduction channel for subsequent fire-driven flooding. Through targeted enrichment of the fire-promoting agent, heat can be precisely released in the target interlayer area, rapidly expanding to the surrounding area after breakthrough, ensuring effective combustion and improving the uniformity and stability of the fire-driven flooding. Furthermore, by monitoring parameters such as temperature, pressure, and gas composition during the combustion process in real time, the gas injection strategy can be dynamically adjusted, making the entire fire-driven flooding process more controllable, ensuring the stable advancement of the thermal front along the oil layer, effectively improving the recovery rate of heavy oil, and enhancing the development effect of heavy oil reservoirs. The method provided by this invention can enhance the ability of heterogeneous reservoirs to actively break through interlayers during fire-driven flooding, further improving the development effect of heavy oil reservoirs. Attached Figure Description

[0041] Figure 1 Flowchart for developing oil reservoir interlayers by injecting combustion aids to burn the oil layer;

[0042] Figure 2 This is a 3D model well location distribution map;

[0043] Figure 3 Schematic diagram of combustion accelerant injection and aggregation;

[0044] Figure 4 The images show the initial stage of air injection ignition, the maximum combustion stage, and the interlayer breakthrough and combustion decay stages (from left to right) of the compound combustion aid composition using potassium chlorate and potassium permanganate as ignition oxidizers.

[0045] Figure 5 The three-dimensional model of the compound combustion aid composition with ammonium nitrate as the ignition oxidizer shows the initial stage of air injection ignition, the maximum combustion stage, the interlayer breakthrough stage, and the combustion decay stage (from left to right).

[0046] Figure 6 This is a three-dimensional model of a compound combustion improver composition with ammonium nitrate as the ignition oxidizer after a fire drive experiment.

[0047] Figure 7The three-dimensional model of the compound combustion improver composition with hydrogen peroxide as the ignition oxidant shows the initial stage of air injection ignition, the maximum combustion stage, the interlayer breakthrough stage, and the combustion decay stage (from left to right).

[0048] Figure 8 The three-dimensional model of the compound combustion aid composition with ammonium nitrate as ignition oxidant and no adsorbent is shown from left to right, including the initial stage of air injection ignition, the maximum combustion stage, the interlayer breakthrough stage, and the combustion decay stage. Detailed Implementation

[0049] The present invention will now be described in detail with reference to embodiments and accompanying drawings, but is not limited thereto.

[0050] The anionic (hydrolyzed) polyacrylamide (Shanghai Experimental) used in the following embodiments of the present invention has an average molecular weight of ≥3,000,000 and a degree of hydrolysis of 25%-30%.

[0051] Example 1

[0052] The method for developing heavy oil through fire-driven interlayers based on formation adsorption combustion improvers includes the following steps:

[0053] (1) 3D model design The internal cavity dimensions of the 3D model are 30 cm × 30 cm × 20 cm, with an overall pressure resistance of 10 MPa. During the reservoir fire flooding process, a one-injection-three-production mode is adopted. Four wells are arranged at the four corners of the cavity, with one well in the lower left corner being a gas injection well, and three wells in the upper left, upper right, and lower right corners being production wells. All four wells are perforated at the top. The temperature and pressure data acquisition system consists of 25 temperature sensors, gas flow meters, and pressure sensors. Two ignition devices are installed within the model, ignition devices 1 and 2 located at temperature sensor 1 (located in well 1) and temperature sensor 13 (center of the model), respectively. The well locations are as follows: Figure 2 As shown.

[0054] (2) Experimental preparation The model was filled with 80-mesh quartz sand. The model had a permeability of 1500 mD, an average porosity of 27.4%, and a crude oil viscosity of 1.3 × 10⁻⁶ m³ / s. 4 mPa·s. In the center of the model, a physical property shield with a length of about 4 cm, a thickness of about 0.5 cm, and a height of about 4 cm is placed obliquely to simulate the interlayer of the oil reservoir.

[0055] (3) Fire drive experiment The fire-drive experiment process includes stages such as injecting oxidizer, gas injection, ignition, and stabilization / displacement. The igniter is preheated. The oxidizer of this invention is injected into the production well. Specifically, the oxidizer uses an AB dual-liquid system, injected sequentially, and mixed underground. Liquid A is the oxidizer liquid, including ignition oxidizer, pH adjuster, polymer adsorbent, solvent distilled water, etc. Liquid B is the fuel emulsion, including main fuel, emulsifier, adsorbent, catalyst, etc. Liquid A (oxidizer liquid) is injected first, and its carried polymers allow it to preferentially enter and remain in the high-permeability layer. Then, Liquid B (fuel emulsion) is injected, and its adsorbent components make the fuel more evenly distributed on the surface of the pores occupied by Liquid A. The two liquids displace and mix with each other in the formation pores. The injection rate is 20 mL / min, and the total injection volume is 0.3 PV. After the oxidizer injection is completed, the ignition agent (a mixture of air and oxygen) is injected into the model at an injection rate of 2 L / min. Ignition device 1 is activated, and ignition begins. After the crude oil is ignited and combustion stabilizes, air is injected, and the injection rate is gradually increased. When the combustion front approaches the point where the model's physical properties obstruct it, ignition device 2 is activated for intermittent ignition, and the injection rate is increased again, with a maximum rate set at 6 L / min. The temperature inside the model is monitored in real time using a temperature field. The production status of oil, gas, and water is recorded. When the temperature inside the model drops significantly, indicating the start of the combustion decay stage, the production well is shut down, and the experiment ends.

[0056] Table 1. Overall Formulation for Preparing Compound Combustion Improver Compositions

[0057]

[0058] (4) Analysis of the temperature field and interlayer breakthrough in fire-driven fire

[0059] Figure 4 The temperature field evolution at different stages of the three-dimensional model fire drive process is shown, namely the temperature change diagrams of the initial stage of air injection ignition, the maximum stage of interlayer combustion, and the combustion decay stage.

[0060] The temperature field distribution indicates that the combustion in the heterogeneous reservoir begins at the initial ignition point near the gas injection well in the lower left corner. Subsequently, the high-temperature zone extends along the main seepage channel towards the center of the model, forming a continuous combustion zone and thermal drive channel. Due to the physical property shielding set in the center of the model to simulate the interlayer structure, when the combustion front approaches the interlayer, the high-temperature zone in the temperature field accumulates in front of the interlayer, and the temperature gradient increases, reflecting the tendency of the interlayer to inhibit and block the propagation of the combustion wave.

[0061] When temperature monitoring indicated that combustion had progressed to the vicinity of the preset second ignition device, relay ignition was initiated, and the gas injection intensity was increased. Experimental results showed that after relay ignition, the local temperature near the interlayer could rise to 350℃, forming a heating zone behind the interlayer. Subsequently, the high-temperature zone diffused towards the back and surrounding areas of the interlayer, indicating that the thermal channel at the interlayer was effectively opened. After entering the combustion stabilization stage, combustion mainly shifted to the lower and middle parts of the reservoir. The sustained high temperature reduced the viscosity and increased the fluidity of the heavy oil, causing it to flow towards the production well. After entering the combustion decay stage, the overall temperature field decreased, the high-temperature zone shrank, and the crude oil combustion intensity decreased until the experiment ended.

[0062] After the experiment, the model was opened and excavated for observation, and it was found that the interlayer (physical property shielding) had cracked. Combining the response characteristics of the temperature field "heat accumulation in front of the interlayer - intermediate ignition and heating - back-side heating and diffusion", it can be considered that the interlayer generates strong thermal stress and internal stress changes under the action of local high temperature, and forms cracks under the coupling effect of combustion gas pressure and thermal expansion, thereby achieving the breakthrough of the interlayer and the connection of the thermal channel.

[0063] (5) Experimental results and analysis of the technical effects of the present invention

[0064] This embodiment employs the AB dual-liquid, sequentially injected, and formation pore-mixed combustion accelerant system described in this invention, combined with dynamic gas injection control and a relay ignition strategy, to achieve continuous propagation of the combustion wave and interlayer breakthrough under interlayer suppression conditions. Its main technical effects are:

[0065] (1) Adsorption enrichment and relay ignition to achieve sandwich layer breakthrough Liquid A, carrying a polymer adsorbent (HPAM), improves the retention and adsorption characteristics of the combustion improver in the porous medium, resulting in a higher retention rate of oxidizing components on the surface of the flow channels. The emulsified / adsorbed components in Liquid B further promote the spreading and adsorption of fuel on the pore surface and at the mineral interface. After the two liquids displace and mix in the formation, a relatively enriched reactant distribution is formed at the adsorption sites near the interlayer. When the combustion front advances to the vicinity of the interlayer and initiates relay ignition, a more intense exothermic reaction occurs at the interlayer, generating localized high temperatures and combustion gas pressure, causing the interlayer to rupture. This opens up previously disconnected heat-driven channels, ensuring the combustion wave continues to advance stably across the interlayer.

[0066] (2) Forming a continuous oxidation combustion process improves flow and harvesting After the interlayer is breached, the combustion chamber expands outward and forms a continuous local heating zone. Experimental records show that the local temperature rises by more than 200°C after the breach. After the intermediate ignition at the interlayer, a local peak temperature of 350°C is generated. Together, they reduce the viscosity of crude oil near the well and in the streamline zone, enhance the fluidity and recoverability of heavy oil, thereby improving the fire-driven development effect and helping to increase the recovery rate.

[0067] However, their response speed and economic benefits have certain limitations. Analysis shows that potassium chlorate and potassium permanganate have low solubility in aqueous solutions, limiting mass transfer and transport. This results in a longer time required to reach an effective concentration during the fire-flooding process, thus reducing the response speed and oil displacement efficiency. Furthermore, potassium permanganate is typically priced above 20,000 yuan / ton, making its application cost high and unsuitable for large-scale industrial applications.

[0068] Based on the above limitations, while keeping the "adsorption and interlayer breakthrough" mechanism unchanged, the oxidant system and catalytic system are further optimized to improve the response speed and reduce the overall cost.

[0069] Example 2

[0070] The method in this embodiment is the same as in embodiment 1, except that in the combustion aid system, liquid A uses ammonium nitrate (NH4NO3) and potassium nitrate (KNO3) as ignition oxidants; liquid B uses a compound emulsion system of petroleum sulfonate and fatty alcohol polyoxyethylene ether, and also adds catalytic / adsorption components such as FeCl3, CuCl2 and nano Co3O4.

[0071] Table 2. Overall Formulation for Preparing Compound Combustion Improver Compositions

[0072]

[0073] Figure 5 The temperature field evolution at different stages of the three-dimensional model fire drive process is shown, namely the temperature change diagrams of the initial stage of air injection ignition, the maximum stage of interlayer combustion, and the combustion decay stage. Figure 6 To mine the three-dimensional model after the fire-drive experiment, a three-dimensional model display diagram of the fire-drive coking zone distribution was obtained.

[0074] The temperature field distribution shows that the combustion of the heterogeneous reservoir fire drive starts from the first ignition position near the gas injection well in the lower left corner. Then the high temperature zone extends along the main seepage channel to the center of the model. When the combustion front approaches the interlayer, the interlayer has a tendency to inhibit and block the propagation of the combustion wave (similar to Example 1).

[0075] As the combustion leading edge advanced close to the interlayer, a significant heat accumulation characteristic appeared on the front side of the interlayer. After initiating relay ignition and implementing dynamic gas injection control, the temperature near the interlayer rose rapidly, with local high temperatures exceeding 400°C at the relay ignition location. Simultaneously, the high-temperature affected zone expanded from the front to the rear of the interlayer, and the temperature field changed from "heat accumulation blocked in front of the interlayer" to "temperature rise response and continuous advancement behind the interlayer," indicating that a permeable heat-driven channel had been formed at the interlayer, enabling the combustion wave to achieve stable advancement across the interlayer.

[0076] Compared with Example 1, the time required for interlayer breakthrough in this example is shorter, indicating that based on the "formation adsorption and enrichment" function of this invention, after optimization of the oxidant and catalytic / emulsification system, the reactants at the interlayer reach the effective concentration faster and the ignition response is more rapid, which can form a local high temperature and high pressure reaction zone earlier, thereby accelerating the rupture of the interlayer structure.

[0077] Compared with Example 1, this example, without changing the concept of the invention, further enhances the following technical effects through optimization of the oxidant and catalytic system:

[0078] (1) Optimization of the oxidant system A higher concentration of ammonium nitrate solution is more conducive to the formation of a uniform oxidant distribution in the porous medium. When combined with the adsorption and blocking effect of HPAM, a more stable oxidation environment can be formed at the adsorption sites near the interlayer, thereby shortening the injection time, increasing the reaction response speed of the interlayer during relay ignition, and thus inducing interlayer rupture more quickly and shortening the breakthrough time.

[0079] (2) Higher overall temperature level and more stable combustion The overall temperature in this embodiment is higher than that in Embodiment 1, indicating that the system has stronger heat release and more sufficient heat supply. After the interlayer is broken, the high-temperature zone can continue to expand behind the interlayer and maintain the continuity of the combustion zone, which helps to avoid the interruption of the combustion leading edge caused by the interlayer, and improves the connectivity of the heat drive channel and the stable propagation capability of the combustion wave.

[0080] (3) Improvement of project economic benefits Components such as FeCl3, CuCl2, and nano-Co3O4 promote oxidation reactions, lower the activation energy, and increase the reaction rate and exothermic efficiency. This allows heavy oil to enter the low-temperature and high-temperature exothermic stages at lower temperatures and release more heat, effectively promoting the combustion reaction of heavy oil.

[0081] By replacing high-cost, low-solubility oxidant combinations with ammonium nitrate, and using common compound petroleum sulfonates and fatty alcohol polyoxyethylene ethers as compound emulsifiers, in conjunction with a metal catalytic system, material costs and formulation constraints can be reduced while maintaining the sandwich breakthrough effect, making it more suitable for large-scale industrial applications.

[0082] Example 3

[0083] The method in this embodiment is the same as in embodiment 1, except that hydrogen peroxide (H2O2) is used as the ignition oxidant in liquid A; diesel is used as the combustion aid fuel in liquid B, combined with a compound emulsion system of petroleum sulfonate and cocamidopropyl betaine, and FeCl3 and nano SiO2 are used as reaction catalysts.

[0084] Table 3 Formulation table for preparing compound combustion improver compositions

[0085]

[0086] Figure 7 The temperature field evolution characteristics of the initial stage of fire-driven ignition, the combustion enhancement and interlayer breakthrough stage, and the combustion decay stage are shown.

[0087] Temperature field monitoring results show that the overall situation is similar to that of Example 1. After the first ignition, the high-temperature zone forms near the injection well and extends into the model along the main seepage channel. The overall temperature level is higher than that of Example 1, indicating that the combustion heat release capacity is enhanced under the formulation conditions of this example.

[0088] When the relay ignition is initiated and dynamically controlled with gas injection, the temperature in the vicinity of the interlayer rises rapidly, reaching a local high temperature of 375°C at the relay ignition location. Subsequently, the high-temperature zone diffuses towards the back of the interlayer, causing a continuous temperature rise response behind the interlayer, indicating that the thermal channel at the interlayer is effectively connected, and the combustion wave propagates across the interlayer. Based on the overall temperature field evolution, the time required for interlayer breakthrough in this embodiment is shorter than in Embodiment 1 but longer than in Embodiment 2, reflecting that the system's ability to trigger enhanced exothermic reaction and breakthrough at the interlayer is between that of Embodiment 1 and Embodiment 2.

[0089] Hydrogen peroxide solution, as a common source of oxidants, has potential engineering advantages such as relatively low raw material prices and easier availability, which can help reduce the material costs of combustion-supporting agent systems. However, it also has characteristics such as sensitivity to storage and preparation conditions and insufficient stability. Furthermore, it may decompose more rapidly and experience activity fluctuations in acidic environments or in the presence of metal ions / catalysts, thus placing higher demands on the safety and process control of on-site preparation, transportation, and injection. Based on this and considering the requirements of engineering applications, the formulation in Example 2 has more comprehensive advantages.

[0090] Based on the above comparison results, and considering the sandwich breakthrough efficiency, temperature field intensity, and system engineering applicability, the combustion aid composition of Example 2 is preferred. Ammonium nitrate and potassium nitrate are used as ignition oxidants in liquid A, and diesel fuel is used in liquid B. A composite petroleum sulfonate and fatty alcohol polyoxyethylene ether are used as emulsifiers, with a small amount of rhamnolipid added to further enhance emulsification and viscosity reduction. FeCl3, CuCl2, and nano-Co3O4 are selected to form a metal catalytic system. The pH of the system is adjusted using HCl.

[0091] Comparative Example 1

[0092] Based on Example 2, we adjusted the combustion aid system by removing the polymer adsorbent, while keeping it the same as Example 2 in all other respects.

[0093] Experimental results show that ( Figure 8The lack of polymer adsorbents reduces the retention and distribution uniformity of the combustion accelerant in the porous medium. Specifically, the absence of adsorbents leads to a decrease in the interaction efficiency between liquid A and liquid B, making it difficult for reactants to form stable local enrichment zones, especially with insufficient accumulation near the interlayer. From the perspective of temperature field evolution, compared to Example 2, the reaction initiation time is significantly prolonged, especially near the interlayer at the combustion front. Due to the lack of adsorption by polymer adsorbents, more combustion accelerant remains in the high-permeability channels, resulting in vigorous combustion in the high-permeability area below the interlayer. However, the accumulation effect of reactants near the interlayer is poor, leading to a weak heat accumulation effect in front of the interlayer, small stress changes, and a prolonged interlayer rupture time. Although the temperature at the interlayer increases after relay ignition, the overall thermal reaction efficiency at the interlayer is still lower than in Example 2, and the efficiency of opening the thermal channels is low, ultimately resulting in a less than expected thermal drive effect. The advancement of the combustion wave is hindered in the interlayer region, affecting the reservoir recovery efficiency.

[0094] Example 4

[0095] The method for developing heavy oil through fire-driven interlayers based on formation adsorption combustion improvers includes the following steps:

[0096] (1) Selection of reservoirs for development: Heavy oil reservoirs were selected according to the above method. The oilfield 1 reservoir in Block A has a burial depth of 734 m, an oil layer thickness of 32 m, and an oil-bearing area of ​​0.032 km². 2 The average porosity is 27.2%, the average permeability is 2380 mD, the initial oil saturation is 0.55, and a continuous distribution of low-physical-property reservoirs is developed within the oil layer. The average thickness of the low-physical-property reservoirs is 0.15 m, and the permeability of the low-physical-property reservoirs is 91 mD. Under the conditions of the oil layer, the crude oil viscosity is 2.3 × 10⁻⁶ m / s². 4 The reservoir's original pressure was 7.14 MPa. The reservoir adopted a reverse nine-point well pattern. The test block was selected, and a row of horizontal wells in the oil layer was used as injection wells. The horizontal wells were located 7 m away from the bottom of the oil layer. The surrounding four rows of wells were production wells.

[0097] The reservoir meets the following conditions: it is a heavy oil reservoir that has undergone multiple rounds of steam thermal recovery and is in the middle and late stages of development. It has a closed structure, a burial depth of 500-1500 m, a permeability of >50 mD, a porosity of >20%, a residual oil saturation of >35%, an oil layer thickness of >10 m, and a crude oil viscosity of 100 mPa·s–50000 mPa·s.

[0098] (2) Obtain reservoir physical and geological parameters. Based on the geological parameters and interlayer type, adjust the composition and dosage of the combustion improver according to the composition of the combustion improver in Table 2.

[0099] (3) Injection of combustion accelerant: Measure and calculate the oil content at the bottom of the formation and calculate the pore volume. For horizontal wells, inject a high-temperature combustion accelerant for 2 days using intermittent injection. The injection pressure is 7.5 MPa, the injection rate is 20 m³ / h, and the total injection volume is 0.3 PV. For blocks with interlayers, the concentration of surfactants and nano-adsorbent particles in the combustion accelerant can be increased by approximately 10-20% to enhance its wetting and adsorption capacity. After injection, the well is closed and allowed to stand for 5-7 days to allow formation permeation. The flowback fluid concentration is 6%, which meets the requirements.

[0100] (4) Injecting air: Through the injection well, a mixture of oxygen and air is continuously injected using an air compressor. The injection volume is 2 PV, the injection pressure is less than the reservoir fracture pressure, and the injection rate is 500 m³ / d.

[0101] (5) Ignition and Combustion: Open the production well and continuously inject air according to the chemical ignition method at a rate of 1000 m / s. 3 / d, igniting crude oil for in-situ combustion. Using monitoring equipment for pressure, temperature, and other parameters, as well as data on production well output, the downhole reaction is monitored in real time, and the gas injection rate is increased to 4000 m³ over time. 3 / d, to maintain the advance of the combustion front.

[0102] (6) The test results show that the injection of the combustion improver successfully ignited the fuel layer. The cumulative oil production over 10 months was approximately 8913 tons, with a stage recovery rate of 7.69%, a significant increase compared to production before fire-driven development. The water cut of the produced fluid decreased from over 95% in the SAGD stage to between 45-75%, a significant decrease compared to production before fire-driven development. The air-to-oil ratio was 2389 m³. 3 / m 3 Based on well logging data, it is estimated that there are 340 interlayers with a thickness greater than 5 cm in the interval. Through analysis of production well fluid production and analysis of wells that have achieved effective fire-drive, about 180 of these interlayers have been successfully breached. The characteristics of these breaches are increased fluid production, higher water cut, decreased oil production, and a clear fluid discharge stage. Afterward, the water cut decreases and the oil production increases.

[0103] The implementation of the development method in the block increased average daily oil production from 0.93 t / d before implementation to the current 1.45 t / d, an increase of 55.9%. The oil production rate has significantly improved. This indicates that the injection of combustion improver has enhanced the effectiveness of fire-driven development.

[0104] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for developing heavy oil in breakthrough fire-driven interlayers based on formation-adsorbable combustion improvers, characterized in that, Includes the following steps: (1) Selection of heavy oil reservoirs for development: (2) Identify and confirm the low-permeability interlayer zone in the reservoir, delineate the target injection area, and divide the injection well group using the original injection and production well network; (3) Inject a combustion-supporting agent with formation adsorption properties into the interlayer area. After the combustion-supporting agent has been adsorbed, pre-inject air is implemented to activate the oxidation capacity of the catalytic combustion-supporting agent. (4) An igniter is continuously injected through an injection well to initiate an in-situ combustion reaction; the igniter is one or a mixture of air and oxygen; (5) Maintain gas injection, monitor combustion temperature and product composition, and control the stable advancement of the combustion front; The combustion aid with formation adsorption properties includes an oxidant liquid and a fuel emulsion. The oxidant liquid includes an ignition oxidant and a polymer adsorbent, wherein the polymer adsorbent is hydrolyzed polyacrylamide. The fuel emulsion includes fuel, an emulsifier, and a catalyst.

2. The method for developing heavy oil in breakthrough fire-driven interlayers based on formation adsorption combustion improvers according to claim 1, characterized in that, The ignition oxidant includes one or more of potassium permanganate, ammonium nitrate, potassium nitrate, hydrogen peroxide, and potassium chlorate.

3. The method for developing heavy oil in breakthrough fire-driven interlayers based on formation adsorption combustion improvers according to claim 1, characterized in that, The fuel is diesel.

4. The method for developing heavy oil in breakthrough fire-driven interlayers based on formation adsorption combustion improvers according to claim 1, characterized in that, The catalyst includes one or more of inorganic salt catalysts and nanocatalysts with formation adsorption properties; the inorganic salt catalyst is a metal chloride, and the nanocatalyst with formation adsorption properties includes one or more of nano Fe2O3, nano SiO2, and nano Co3O4.

5. The method for developing heavy oil in breakthrough fire-driven interlayers based on formation adsorption combustion improvers according to claim 1, characterized in that, The emulsifier includes one or more of the following: compound petroleum sulfonate, cocamidopropyl betaine, sodium dodecylbenzene sulfonate, and rhamnolipid.

6. The method for developing heavy oil in breakthrough fire-driven interlayers based on formation adsorption combustion improvers according to claim 1, characterized in that, The combustion aid with stratum adsorption properties further includes a solvent and a pH adjuster; the solvent is water, and the pH adjuster is hydrochloric acid; the pH of the combustion aid is 4.0-6.

0.

7. The method for developing heavy oil in breakthrough fire-driven interlayers based on formation adsorbent combustion improvers according to claim 6, characterized in that, The combustion aid comprises, by mass percentage: 10-30% igniting oxidant, 0.5-2% polymer adsorbent, 20% fuel, 2-3% emulsifier, 0.01-0.3% catalyst, 0.1-3% pH adjuster, and the balance being water.

8. The method for developing heavy oil in breakthrough fire-driven interlayers based on formation adsorption combustion improvers according to claim 1, characterized in that, The injection method described in step (3) is to first inject the oxidant solution, then inject the fuel emulsion, and inject intermittently for 3–6 hours each time; the injection pressure is 1.1–1.3 times the formation pressure; the injection rate is 20–50 m³ / h / well, and the total injection volume is 0.2–0.5 PV; After injection, the well is closed and left to stand for 5–7 days to allow the formation to absorb the substance.

9. The method for developing heavy oil in breakthrough fire-driven interlayers based on formation adsorbent combustion improvers according to claim 1, characterized in that, The specific steps of step (4) are as follows: a mixture of oxygen and air is continuously injected through the injection well, the injection volume is greater than 2 PV, the injection pressure is less than the reservoir fracture pressure, and the injection speed is 500-1000 m³ / h; in the early stage of the ignition reaction, the downhole temperature and reaction are monitored in real time using temperature probes and pressure monitoring equipment. When the combustion front reaches the vicinity of the interlayer, a secondary ignition is carried out near the interlayer to form a high-pressure combustion environment to ensure the interlayer fracture.

10. The method for developing heavy oil in breakthrough fire-driven interlayers based on formation adsorbent combustion improvers according to claim 1, characterized in that, In step (5), the combustion leading edge temperature is maintained in the range of 350℃–650℃; the advancing speed of the combustion leading edge is controlled in the range of 0.5–2.5 m / h.

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